The world number one continued her dominance of the tournament, winning the same slam trophy three years in a row for the first time with a 6-3 6-3 victory.

Williams did not drop a set all tournament and hit 29 winners to Wozniacki's four - all but one of which were aces.

The Dane had hoped she would be more ready for the occasion five years after her first slam final here, when she lost to Kim Clijsters, but she was comprehensively second best.

It has been a tough season for Williams by her sky-high standards, the American failing to make it past the fourth round at any of the first three slams.

There was also the bizarre spectacle of her having to retire during a doubles match at Wimbledon when she appeared barely able to hold a ball - the explanation of a viral illness was treated with some scepticism.

The emotion for Williams was clear and she struggled to hold back tears as she explained her feelings at winning a sixth US Open title 15 years after her first.

"It was a really wonderful feeling," said Williams, who also collected a cheque for four million US dollars, the biggest in tennis history.

"It was a wonderful finish, I couldn't have thought of any better way. Congratulations to Caroline, she's known what a struggle it's been for me, we text almost every day.

"I know you're going to win (a slam) very soon, maybe even in Australia. I've got to go home and get fit again so I can get ready for you."

Williams was then joined on court by Evert and Navratilova, who presented her with an 18-carat gold Tiffany bracelet to mark her achievement.

Addressing Williams, Wozniacki said: "You really deserved it today, you played better than me. You're an unbelievable champion, an inspiration to me on and off court. You're an unbelievable friend and you definitely owe drinks later."

There was much at stake for both women, although Wozniacki had proved a great deal whatever happened in the match.

The pair's friendship has grown closer this summer, with Williams helping Wozniacki to get over the shock of her split from Rory McIlroy during a week's holiday together in Miami.

Wozniacki had only won one of their nine previous matches, but she had pushed Williams close in clashes in Montreal and Cincinnati last month.

Two double faults in her first service game was not a great way to start for Wozniacki and Williams took advantage to take a 2-0 lead.

But Williams looked edgier than she had in her previous matches and four errors handed the break straight back.

The American was all over Wozniacki's serve and after three attempts she still had not held.

Her weaker forehand was being exposed and, when Williams put a better service game together to lead 5-2, Wozniacki was in trouble.

Consistency is usually the bedrock of her game, but, whether it was the occasion or the pressure of playing Williams, she was far from her best.

The 24-year-old did at least save a set point and hold serve for the first time, but Williams finished it off with a backhand winner after one of the best points of the match.

A tally of one winner and 10 unforced errors was certainly not going to help Wozniacki follow in McIlroy's footsteps and become a major champion.

Wozniacki was not as positive in her play as she had been throughout the tournament, particularly in her fourth-round win over Maria Sharapova, and Williams was dictating while her opponent scampered around the baseline.

Had Wozniacki been broken for 3-0, the match would have been all but over before the hour mark, but she saved a break point to stay just about in contention.

However, Williams had well and truly found her serve after the shaky start and did not give Wozniacki a glimpse of a break back.

The 24-year-old finally hit her first winner off the ground in the ninth game, but three points later Williams clinched victory when Wozniacki drove a backhand long.

The American, who turns 33 later this month, dropped to the ground in delight before sharing a hug with Wozniacki.